do I need the hardrive and dvd attached in order to boot the xbox into a screen?

What screen are you trying for?

With or without a modchip, when booting with no drives you'll see the flubber animation then the big 'X'. From there it will most likely either stay there frozen or give you the error screen.
If you have a chip installed and boot with the flashios it will boot straight into the blue flash bios menu, no drives required.

You need both with a retail bios but newer hacked bios's will allow you to boot without the dvd drive and hdd but will just hang.

Caster.

i'm troubleshooting my soldering and its getting to be a pain by putting the unit back together everytime I test. So far, it tries to boot twice--while the smartxx mod chip flashed blue twice, and then I get a blank screen, so its got to be my soldering?